1. Field of the Invention
The present invention relates to a halftone dot recording method and a halftone dot recording apparatus for recording a total image which is formed by editing a plurality of types of original image components by selecting different types of halftone dots for the respective original image components on a photosensitive material.
2. Description of the Background Art
In a process of prepressing a total image which is formed by arranging a plurality of original image components in combination, halftone dots having different shapes are generally selected for the respective original image components, in order to improve a visual effect in a final print of the total image. In order to record such a total image by selecting a plurality of types of halftone dots for the respective components, however, an accurate operation is required with a large number of steps. To this end, U.S. Pat. No. 4,727,430 in the name of the assignee, for example, discloses a technique which is capable of recording a plurality of types of halftone dots having different shapes for respective original image components through single scanning in an image recording apparatus such as a color scanner. This technique is adapted to previously record a plurality of types of halftone dot signals expressing halftone dots of different shapes in a halftone dot signal memory and to appropriately select one from the plurality of types of halftone dot signals in a process of recording a total image on the basis of signals designating recording positions of respective original image components, thereby recording halftone dots.
In order to further improve the visual effect in the final print, it may be desirable to properly change not only the shapes of the halftone dots but screen rulings or screen angles in response to the original image components. In either case, it is necessary to also change the minimum repeating units for the halftone units following the changes in the types of the halftone dots. In the technique disclosed in the aforementioned patent, however, the plurality of types of halftone dots are merely different in dot shapes from each other, with a common minimum repeating unit. Thus, this technique cannot satisfy the aforementioned requirement.